I do not remember from where or when I took possession of this screw. It may have come in a stripped lower, or maybe in an assembled lower. It's a trigger-creep screw, but unlike any I have ever seen before or since I got it. I have several similar screws now, but none have the plastic bumper on them as does this one. Would like to discover who makes this one, and get several more. Wondering if any of our august membership can identify its source or who might make it. The threaded portion is half an inch long; the entire length is 9/16" long. Thanks.